Golf club head and method of manufacture

Abstract

An iron-type golf club and a method of creating the iron-type golf club including the steps of forming a club head blank having a blank loft, a blank head weight of 345-400 grams, and an external sacrificial region having an ESR thickness, an ESR sole portion, an ESR face portion, and an ESR leading edge portion. A finished club head is formed having a finished club head weight of less than 310 grams by machining off an ESR removed mass from at least a portion of the external sacrificial region including at least a portion of the ESR sole portion, a portion of the ESR face portion, and a portion of the ESR leading edge portion.

We claim: 
     
       1. A method of creating an iron-type golf club, comprising:
 a) forming a club head blank having a blank loft, a blank lie angle, and a blank head weight of 345-400 grams, wherein:
 (i) the club head blank includes a body including a hosel, a heel portion, a sole portion, a toe portion, a top-line portion, a face portion, and a leading edge joining the face portion and the sole portion, wherein the sole portion extends rearwardly from the leading edge; 
 (ii) the club head blank includes an external sacrificial region having an ESR thickness, an ESR sole portion, an ESR face portion, and an ESR leading edge portion; 
 
 b) forming a finished club head having a finished club head weight of less than 310 grams by machining off an ESR removed mass from at least a portion of the external sacrificial region including at least a portion of the ESR sole portion, a portion of the ESR face portion, and a portion of the ESR leading edge portion, wherein:
 (i) less than 70% of the ESR removed mass is removed from the ESR face portion; 
 (ii) at least 20% of the ESR removed mass is removed from the ESR sole portion; and 
 (iii) at least 50% of the ESR leading edge portion is machined to produce a finished leading edge radius. 
 
 
     
     
       2. The method of  claim 1 , wherein a majority of the portion of the ESR leading edge portion that has been machined is adjacent to a portion of the ESR face portion that has been machined. 
     
     
       3. The method of  claim 2 , wherein the majority of the portion of the ESR leading edge portion that has been machined is adjacent to a portion of the ESR sole portion that has been machined. 
     
     
       4. The method of  claim 3 , wherein at least 70% of the ESR leading edge portion is machined. 
     
     
       5. The method of  claim 3 , wherein the ESR face portion covers at least 1800 mm 2 , the ESR sole portion covers at least 900 mm 2 , the ESR leading edge portion covers at least 50 mm 2 , the ESR thickness is less than 2.5 mm, at least 0.25 grams of the ESR removed mass is removed from the ESR leading edge portion, at least 2.5 grams of the ESR removed mass is removed from the ESR sole portion, and at least 5.0 grams of the ESR removed mass is removed from the ESR face portion. 
     
     
       6. The method of  claim 5 , wherein the ESR removed mass removed from the ESR sole portion is at least 30% of the ESR removed mass removed from the ESR face portion. 
     
     
       7. The method of  claim 6 , wherein the ESR removed mass removed from the ESR sole portion is no more than 125% of the ESR removed mass removed from the ESR face portion. 
     
     
       8. The method of  claim 6 , wherein 15-45% of the ESR removed mass is removed from the ESR sole portion. 
     
     
       9. The method of  claim 3 , wherein the club head blank has a club head blank CG location and the finished club head has a finished club head CG location, and a shortest distance from the club head blank CG location to the finished club head CG location is no more than 2 mm. 
     
     
       10. The method of  claim 2 , wherein the external sacrificial region includes an ESR neck blend portion. 
     
     
       11. The method of  claim 10 , wherein a portion of the ESR neck blend portion extends to an elevation above a ground plane that is greater than a height of a center of gravity of the finished club head, and at least a portion of the ESR neck blend portion located above the center of gravity of the finished club head is machined off to create the finished club head. 
     
     
       12. The method of  claim 10 , wherein at least 0.25 grams of the ESR removed mass is removed from the ESR neck blend portion, and wherein the ESR removed mass is removed from the ESR neck blend portion is greater than the ESR removed mass is removed from the ESR leading edge portion. 
     
     
       13. The method of  claim 2 , wherein the club head blank includes an internal sacrificial region, and the step of forming the finished club head includes machining away a portion of the internal sacrificial region to form a sole portion void, wherein the sole portion void has a void length that is at least 50% of a sole length. 
     
     
       14. The method of  claim 1 , wherein the blank leading edge has a blank leading edge radius, and the finished leading edge radius is at least 25% less than the blank leading edge radius. 
     
     
       15. The method of  claim 14 , wherein the finished leading edge radius is 25-50% less than the blank leading edge radius. 
     
     
       16. The method of  claim 10 , wherein a portion of the ESR face portion is machined off first producing a step discontinuity with at least a portion of the ESR neck blend portion, then in a single orientation and with a single machine tool at least a portion of the ESR sole portion, a portion of the ESR leading edge portion, and a portion of the ESR neck blend portion, including the step discontinuity, are removed. 
     
     
       17. The method of  claim 16 , wherein the single machine tool is a ball end mill. 
     
     
       18. The method of  claim 17 , wherein the step of machining off at least a portion of the ESR sole portion and a portion of the ESR leading edge portion is performed with the club head blank held in a single orientation, and a hosel centerline axis establishes a vertical shaft axis plane containing the hosel centerline axis, a vertical front-to-rear plane is perpendicular to the vertical shaft axis plane, and a tool path plane is vertical and within a path angle of the vertical front-to-rear plane, wherein during the step of machining the ESR leading edge portion the machine tool traverses the ESR leading edge portion along a machine tool path that lies between the vertical front-to-rear plane and the tool path plane, and the path angle is no more than 35 degrees. 
     
     
       19. The method of  claim 18 , wherein the finished leading edge radius is 1.0-4.0 mm and the ball end mill has a tool diameter of 2 mm or less. 
     
     
       20. The method of  claim 19 , wherein the ball end mill machining of the ESR leading edge portion is carried out with a step-over distance that is less than the finished leading edge radius, and produces a scallop height of less than 50% of the finished leading edge radius.